This invention relates to a rotary tool assembly having a removable working element, and to a method of making such a rotary tool assembly.
A rotary tool such as a drill bit is customarily formed of an integral or permanently connected shank, received in a chuck which is rotated in a conventional manner by an electric motor or other means. The integral assembly adds unnecessary expense to the tool, due both to the expense of fabricating the shank and the cost of materials, the latter being particularly applicable when the tool has an integral cutting edge which requires the use of expensive materials for the entire tool. Depending upon the particular type of tool, diverse machining operations must be performed on the single piece which also adds to the manufacturing expenses.
Other existing tools, typified by the well-known socket wrenches, have utilized working elements which are removable from a shank by hexagonal or square male-female joints. However, the particular means of interconnection between the shank and the working element in such tools differs from and is in some respects less satisfactory than the particular interconnection means of the present invention.
It has also been known to provide a conical taper fit between a working element and a shank, the angle of the conical taper being selected so that the working element and the shank remains frictionally affixed, both longitudinally and rotationally, during normal use of the tool.
An object of this invention is to provide an uncomplicated, inexpensive but quite effective rotary tool assembly having a removable working element, and to a method of making such a rotary tool assembly.
The tool assembly of this invention includes a shank and a working element which is removable from and unbonded to the shank. The shank has a driven end portion which is connected to a drill or other suitable drive means, and a tool-receiving end portion to which the working element is removably connected. The tool-receiving end portion of the shank is provided with longitudinal slots, each of which has side walls and a bottom wall which is located radially outwardly from the central longitudinal axis of the shank, and the slots form a taper between them. The working element has driven end segments which are received by the slots of the shank. The driven end segments each contact the bottom wall of one of the slots to prevent radial movement between the working element and the shank; and, each of the driven end segments also contacts one of the side walls of its respective slot to receive torque delivered to the working element by the shank.
The tool-making aspect of the invention involves separate formation of a shank and a working element of the type described above, and placement of the working element or the shank to bring them into the specified relationship wherein the radially innermost surfaces of the driven end segments of the working element are received between the side walls of the respective slots and in contact with the bottom walls of the slots so that the tool is radially positioned on the shank and in torque-receiving relationship with respect to the shank.